The industrial developments contribute significantly to the economic growth of a country. However, with the industrial growth, risk to the environment increases and an adequate balance between the two should be a guiding principle. But, caring for environment is an expensive activity and often overlooked. Industries are normally interested in short-term gains and therefore environmental care is the last item on their agenda – mostly, out of some compulsions. In developing countries where economy override environment, the degradation of once pristine marine areas is common. The productive coastal habitats such as mangroves, sea-grass beds, and mudflats are destroyed or reclaimed to meet ever-increasing demands of the society. Sewage and industrial effluents are indiscriminately released to the sea in vary areas where we swim and fish with total disregard to the capacity of the environment to digest the waste. Several such sites of degraded marine ecology are identified around our coastline. We are learning from the industrialized world, albeit slowly, the perils of environmental neglect. The learning process has made some of us conscious of ‘Environmental care' as a strategy that needs to be enforced in all seriousness. We have a long way to go but there seems to be some light at the end of the tunnel. Unless we put in vigorous efforts in caring for the environment much of our marine wealth will be lost to our future generations.

India on her coastline has good number of unique environments that need to be cared and nurtured. One such unique habitat is the Gulf of Kachchh, which occupies an area of 7,350 sq km in the state of Gujarat, India. Its depth extends from less than 20m at the head (eastern end) to about 60m at the mouth (western end) (Figure 1). All along the coast, a few rivers drain into the Gulf but they carry only a small quantity of freshwater during the brief monsoon. Rainfall (~50 cm/yr) is unevenly distributed and often scanty, but is the ultimate source of freshwater to the region. The climate of the region varies between extremely arid (dry) in the northern Gulf and semi-arid in the southern Gulf. The water in all depths is almost homogeneous if we consider temperature and salinity as parameters. The excess of evaporation over precipitation makes the Gulf more saline than the Arabian Sea to which it is connected. Another unusual feature is the tides. The difference between high and low tide is to the extent of about 3.1m at Okha, 4.7m at Sikka, 5.8m at Kandla and 6.4m at Navlakhi. The typical bathymetry, funnel shape of Gulf, coastal configuration, orientation of the coast all contribute to the increasing tidal range in to the Gulf. During low tide, vast areas submerged during high tide are exposed teaming with diverse life forms from a variety of sea anemones, mudskippers, crabs to clusters of birds active in feeding on the exposed biota.

Large number of islands, coral reefs, marshy islands, mangroves, sandy stretches, creeks and bays along the coast of the Gulf provide diverse habitats for marine flora and fauna leading to high biodiversity. This area, in fact, is considered to be one of the richest marine habitats along the west coast of India. To protect this bio-rich domain several stretches between Okha and Jodia including coral reefs and mangrove habitats have been declared as Marine Sanctuary (458 km² ) and Marine National Park (163 km²). However, here too the conflict between development and conservation is acutely perceptible and is growing with setting-up of industries, ports and salt works often at the expense of fragile coastal ecology. An industry manufacturing soda ash and a variety of other products at Mithapur is perhaps the first major industry established along the southern Gulf. Undoubtedly, the industry contributed immensely towards the economic and social development of the Mithapur region. However, the Gulf had to pay the price. About 10 km² of the marine protected area has been considerably degraded due to the settlement of solids associated with the effluent of the industry. Another example of myopic approach was the leasing of the Gulf area for mining coralline sand to a cement industry at Sikka. Though the lease was terminated in early eighties, the dredging of sand for over a decade that formed the raw material for the manufacture of cement, caused severe ecological destruction particularly of corals and once flourishing pearl oyster industry was totally wiped off.

Recent major development along the southern Gulf is the establishment of India's largest refinery at Sikka. Another refinery is under construction at Vadinar. Availability of relatively deep waters near the southern shore and protection from monsoon waves has made the Gulf attractive for the import of crude oil through Very Large Crude Carriers (VLCCs) and unloading the cargo via Single Point Mooring (SPM) systems to shore-based tank farms. Four SPMs with a potential to handle about 50 million tons per year (t/y) of crude oil are already operational and a few more are being considered. The traffic of crude oil is projected to increase from the present of 40 million t/y to over 70 million t/y by 2007. With this, the traffic of VLCCs is expected to go up to roughly 500 per annum by 2007 apart from the traffic of tankers carrying petroleum products. This multifold increase in traffic of crude oil and its products enhances the risk of oil spills due to tanker accidents, hose ruptures, sub-sea pipeline leakage, operational discharges etc. If a large spill occurs, the Gulf ecology particularly of the intertidal and subtidal nearshore habitats will be under high risk. Another major development is the establishment of a multi-cargo port at Mundra on the northern shore of the Gulf. With the establishment of refineries and port, the coastal area of the Gulf is projected to have a variety of downstream and other industries which undoubtedly would impact the fragile marine ecology of the Gulf if proper environmental planning aimed at protecting this rich biodiversity is not conceived and implemented.

One of the key water quality parameter that is intimately linked with the health of marine biota is Dissolved Oxygen (DO). The oxygen dissolved in water is as vital for most aquatic organisms as oxygen in air for terrestrial animals. DO in water is replenished through photosynthesis by algae present in natural waters, dissolution from atmosphere and addition of oxygen rich water where there is inflow from natural sources such as rivers. Simultaneously, the DO is consumed during decomposition of organic matter present in water or added through domestic sewage/industrial effluent etc, and respiration by aquatic flora and fauna. Thus, equilibrium is maintained between the replenishment of DO and its consumption. In natural waters where there are no polluting releases the rate of consumption of DO is lower than the rate of replenishment resulting in maintenance of its adequate concentrations in water for healthy aquatic life. Release of anthropogenic organic matter consumes DO and if the load is high, consumption of DO is more than that the water body can replenish creating low concentrations in water. In extreme cases this may lead to onset of septic conditions with emissions of mal-odorous thereby causing fish-kills and severe degradation in ecological quality. It is difficult to arrive at the threshold limit of DO for aquatic life, since environmental conditions, waste loading and natural levels of DO vary considerably and the existent composite aquatic life has variable demand for DO depending on their composition, age, activity, nutritional status etc. However, it has been observed that below 2 ml/l concentration of DO, good and diversified aquatic life may not be maintained since feeding of many organisms is diminished or stopped and their growth is retarded at low DO levels. Embryonic and larval stages of aquatic life are especially vulnerable to reduced conditions and may also result in retarded development and even partial mortality. Although there is no unanimity on the level of DO that shall be maintained in coastal waters and estuaries conducive to biota, it is considered that the level should not fall below 3 ml/l for prolonged periods. Based on the designated use of water in the coastal regions, the Central Pollution Control Board (CPCB) had set guidelines for water quality criteria (Table 1) based on DO and biological oxygen demand (BOD). BOD provides a quantitative measure of organic matter in water that can potentially consume DO.

Table 1 - Primary water quality criteria

NIO has been conducting periodic investigations in the Gulf for the past 27 years. Using this database generated over nearly 3 decades an attempt has been made to predict the amount of additional BOD that can be digested by different segments of the Gulf (Okha, Salaya, Vadinar, Sikka, Navlakhi, Kandla) while maintaining DO at acceptable levels.

The database indicates that in the Gulf, the BOD varies from 0.1 to 3.3 mg/l during pre-monsoon and from 0.1 to 5.3 mg/l during post-monsoon. The high values are generally confined to Vadinar and Navlakhi where anthropogenic perturbations are relatively high. On the whole, the average BOD is high during post-monsoon (1.2 to 2.7 mg/l) compared to pre-monsoon (0.7 to 1.7 mg/l) (Figure 2). These BOD values are in the range normally recorded for healthy coastal waters and prevailing BOD loading on the Gulf through various sources seems to be effectively consumed.

Figure 2 - Max/Min/Av values of BOD and DO

The percentage saturation value, which takes into account variation of DO with salinity and temperature, is a better measure of DO in marine environment. The DO in the Gulf is close to saturation (75% to 109%) once again supporting the above assumption of efficient consumption of prevailing organic loads. Also, the DO is markedly higher than the saturation level recommended (60%) by the CPCB for ecologically sensitive areas (SW1 type) (Table 2).

Table 2 - Average DO concentration

The average levels of DO at various locations in the Gulf as well as the DO in excess of designated best use are illustrated in Figure 3. Thus for instance, the minimum DO recommended for harbour waters (SW-4) is 3 mg/l. Based on this criteria Mundra harbour has 3.5 mg/l additional DO available for utilization. Bedi and Positra being ecologically sensitive zones (Marine National Park and Marine Sanctuary) are considered to be in SW1 category and have about 1.9 and 1.6mg/l additional DO above the minimum recommended by CPCB. The other port regions (Okha and Kandla) have relatively low DO suggesting careful consideration for future releases of BOD. Salaya-Sikka segment is ecologically sensitive needing SW-1 quality. Figure 3 indicates that the region may not assimilate additional BOD.The assessment based on DO-BOD model is a simplistic approach to minimize impact of anthropogenic releases of dissolved organic matter that can be biochemically oxidized in the marine environment. In practice however, the effluents are complex and contain several contaminants that can be harmful to marine biota even at trace levels. Thus for example, apart from organic matter, release of domestic wastewater introduces microorganisms and viruses some of which remain viable for days in seawater. Reports indicate that organisms such as corals in areas affected by sewage develop diseases even when the DO levels are optimum. Similarly, industrial return seawater used for cooling may not contain serious contaminants but local biota is subject to higher temperature that is known to result in ecological modifications. Hence, the best strategy for the Gulf is to permit only those industries that do not release effluent to the Gulf and releases such as thermal discharges that are unavoidable are allowed only after proper investigations to identify location of release in a manner that the ecology is not adversely affected. Further, in view of large-scale transport of crude oil and its products, a strategy needs to be in place to minimize risk of accidental release of petroleum and to combat a spill should it occur in an unusual situation.